Fixes error found by gofuzz and reports line-column numbers for lexer/parser errors

[gitlw]

• added line and column number to lexer and items
• checking item error from lexer and return immediately when found
• enforcing 100 chars
  fixes Input found by gofuzz can crash the alpha server #2900

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This change is 

[manishrjain]

Few comments. Also, avoid checking for line and column number in existing tests. Instead, create a few tests just for that.

Reviewed 7 of 7 files at r1.
Reviewable status: 6 of 7 files reviewed, 4 unresolved discussions (waiting on @codexnull, @gitlw, @manishrjain, and @srfrog)

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gql/parser_test.go, line 2729 at r1 (raw file):

	require.Error(t, err)
	require.Contains(t, err.Error(),
		"line 4 column 35: Unrecognized character in lexDirective: U+002C ','")

Let's not check for line and column here. If we modify the way we count a bit, we'd need to keep on modifying these tests.

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lex/lexer.go, line 51 at r1 (raw file):

func (i Item) Errorf(format string, args ...interface{}) error {
	return fmt.Errorf("line %d column %d: "+format,
		append([]interface{}{i.line, i.column}, args...)...)

, i.line, i.column, args... should work. You don't need the append.

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lex/lexer.go, line 188 at r1 (raw file):

		Typ: ItemError,
		Val: fmt.Sprintf("while lexing %v at line %d column %d: "+format,
			append([]interface{}{l.Input, l.Line, l.Column}, args...)...),

No need for append.

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lex/lexer.go, line 329 at r1 (raw file):

// isEndOfLine returns true if the rune is a Linefeed or a Carriage return.
func isEndOfLine(r rune) bool {

Maybe consolidate this func being used across multiple pkgs into one lex pkg.

[gitlw]

Reviewable status: 3 of 10 files reviewed, 4 unresolved discussions (waiting on @codexnull, @manishrjain, and @srfrog)

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gql/parser_test.go, line 2729 at r1 (raw file):

Previously, manishrjain (Manish R Jain) wrote…

Let's not check for line and column here. If we modify the way we count a bit, we'd need to keep on modifying these tests.

Done.

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lex/lexer.go, line 51 at r1 (raw file):

Previously, manishrjain (Manish R Jain) wrote…

, i.line, i.column, args... should work. You don't need the append.

It does not work without append.

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lex/lexer.go, line 188 at r1 (raw file):

It does not work without append.
It does not work without append.

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lex/lexer.go, line 329 at r1 (raw file):

Previously, manishrjain (Manish R Jain) wrote…

Maybe consolidate this func being used across multiple pkgs into one lex pkg.

Done.